Chain saws are currently employed to fell trees and trim branches, and to reduce the trees and branches to logs of manageable size. Chain saws include an engine or motor enclosed within a housing, and a thin bar extending outwardly from the housing upon which an endless chain slides. Chain saws may be powered by gasoline or diesel engines or electric motors, and are employed in situations where the depth of cut is more than a few inches and a wide kerf is desirable or acceptable. Commercial applications generally require more heavy duty chain saws with longer and wider bars and correspondingly longer and wider chains, while consumer applications typically have shorter and thinner bars and chains.
Through use, the cutting surfaces of the various teeth along the chain become dulled and worn. This requires additional pressure on the chain saw to effect the desired cut, can generate excessive and dangerous heat, and generally makes it difficult to cut through the wood. It is thus necessary to periodically sharpen the cutting surfaces of the teeth to maintain efficiency in the cutting operation. The saw chain comprises a series of right-hand cutting links and left-hand cutting links, alternatively positioned around the chain. The cutting portion of each link includes a cutting tooth typically with a first surface perpendicular to the saw kerf and a second surface parallel to the saw kerf. The two cutting surfaces normally join at right angles in a chisel-bit-type cutter tooth, or a single curved surface may be used which extends into the two planes perpendicular and parallel to the saw kerf. An upstanding portion, typically referred to as a depth gauge, projects upwardly in front of the cutting surfaces on each link. The forward edge of the cutting surfaces are typically ground at a predetermined rake angle, typically 35 degrees, with respect to a line drawn perpendicular to the length of the cutting link. Detailed illustrations and descriptions of cutting links for conventional chain saws are found for example in U.S. Pat. Nos. 5,156,071 and 4,463,499.
The unique shape of the cutting teeth on a chain saw and their location on separate links in a chain requires special sharpening tools in order to accurately and quickly sharpen the blade.
Large scale commercial operations can sometimes afford extra chains which can replace worn chains, and/or expensive (and complex) sharpening machines and dedicated personnel to operate the machines. However, many operations, as well as typical consumers, are not so well organized and funded. One tool which has been used by these individuals is a round or triangular file which is manually drawn along the cutting surfaces of the teeth. The file is drawn back and forth until the proper hone of the surface is obtained. This can be a tedious and time-consuming process, and many consumers are not skilled in properly drawing the file back and forth to create a proper rake angle, and a rake angle which is the same for the right and left facing teeth.
A number of mechanical saw sharpeners have also been developed in an attempt to reduce the labor and improve the accuracy with which the saw chains are sharpened. One such sharpener is shown in U.S. Pat. No. 4,463,499, where a rotary burr formed of hardened steel and affixed to a hand crank can be manually rotated and brought into position within a cutting tooth to sharpen the tooth. Another sharpener is shown in U.S. Pat. No. 5,107,726 where a circular file is rotatably mounted within support members and can be manually brought into contact with the teeth and rotated until the proper hone is achieved.
Still another sharpener uses a rotating cylindrical stone sized so that the cylindrical surface forms the cutting edges on the chain saw tooth. Other sharpeners employ grindings wheels which are shaped to form the proper cutting surfaces. One such sharpener is shown in U.S. Pat. No. 5,156,071 where a sharpening tool with a flat circular plate is affixed with a circumferential abrasive bead having a convex profile. The convex profile of the bead fits into the space between the depth gauge and the cutting tooth of a chain saw blade and is mechanically rotated to form the cutting tooth.
In the above sharpeners, the chain saw bar is initially grasped and held stationary, and the sharpening tool is brought into contact with an appropriate cutting tooth. Because the cutting teeth alternate in angle, that is, a right-facing cutting tooth with a right-facing cutting surface alternates with a left-facing tooth with a left-facing cutting surface, the sharpening tool has to be manually aligned with the particular cutting surface to be sharpened. Some sharpeners successively sharpened all the right-facing cutting teeth with right-facing cutting surfaces, and then all the left-facing teeth with left-facing cutting surfaces. Other sharpeners allow the sharpening tool to be manually positioned in alternating right and left orientations for cutting each successive (right or left-facing) tooth.
While many chain saw sharpeners have been developed in an attempt to quickly and easily sharpen the cutting teeth along a chain saw, it is believed that heretofore these sharpeners have still required an unacceptable amount of user/operator time and effort, particularly in adjusting and positioning the sharpener correctly with respect to a cutting tooth, sharpening the tooth, and then incrementing the chain to the next tooth. It can be difficult for the user to determine when the proper hone of a tooth has been reached. It is also believed that because of the user involvement in the sharpening process, it can also be difficult to consistently and repeatably obtain a proper hone to the cutting surfaces, both in rake angle and from tooth-to-tooth.
Applicant further believes that heretofore automated chain saw sharpeners have not been developed mainly because of the problem of compensating for the length and width of the chain and the distance between cutting teeth, which can vary between manufacturer-to-manufacturer, and sometimes between model-to-model. The bevel and depth of each tooth can also vary in the same way. While manual sharpeners generally allow the user to determine the proper angle and depth of the cutting tooth, and when the sharpening process is complete (that is, when all the teeth have been sharpened), this appears to have discouraged the development of a more automated process, at least until the present invention.
Applicant therefore believes there is a demand in the industry for a more automated chain saw sharpener which allows the user to quickly and easily sharpen the entire chain on the saw, even if the user does not have expertise in chain saw sharpening. It is also believed there is a demand in the industry for a chain saw sharpener which easily accepts a wide variety of chain lengths, widths, bevels, depths, and tooth-to-tooth distances, so that the sharpener can be used in both commercial and consumer applications. Further, it is believed there is a demand in the industry for a chain saw sharpener which is relatively simple in construction and in operation, is portable, and is relatively inexpensive to purchase and maintain.